1. Field of the Invention
The present invention relates to a differential amplifier circuit configured to amplify a difference between two input voltages.
2. Description of the Related Art
Differential amplifier circuits are widely used in various electronic devices. In particular, a differential amplifier circuit is able to perform analog signal processing with high accuracy by being applied a negative feedback. Therefore, the differential amplifier circuit has become an essential technology in the development of electronic devices of today.
The differential amplifier circuit has a function of amplifying a difference between two input voltages, and is constantly being required to have a lower current consumption, a smaller size, and a lighter weight, as represented by mobile electronic devices driven by batteries.
In FIG. 3, a related-art differential amplifier circuit is illustrated. The related-art differential amplifier circuit includes an amplifier circuit 1 in a first stage, which is configured to amplify a voltage difference between two input terminals IP and IN, amplifier circuits 2 and 6 in a second stage, which are configured to amplify a voltage difference between output terminals OP and ON of the amplifier circuit 1, an output transistor 7 of a PMOS transistor that has a gate controlled by output GH of the amplifier circuit 2, and an output transistor 3 of an NMOS transistor controlled by output GL of the amplifier circuit 6.
In the differential amplifier circuit as described above, the output transistors 3 and 7 are arranged to attain low impedance at an output terminal OUT. Further, the amplifier circuits 2 and 6 are arranged in the second stage to facilitate setting of a bias for operation of the output transistors 3 and 7.
However, the differential amplifier circuit described above includes three amplifier circuits, and thus has a downside in that the current consumption and a circuit area are increased.